This invention relates generally to the field of mobile equipment used to move or remove dirt and to level ground surfaces over relatively large areas, and more particularly to such equipment which are wheeled constructions pulled behind motorized vehicles, such being commonly referred to as dirt scrapers, box blades, box scrapers, pull-behind scrapers, levelers or the like. More particularly, the invention relates to such equipment which are provided with stabilizer means to reduce negative effects caused by uneven terrain, these negative effects known by such terms as bounce, walking or rocking, where the stabilizer means is damped to reduce vertical motion.
Dirt scrapers are used to remove large quantities of dirt in a relatively rapid manner and/or to level large areas of ground with relatively high precision. The scrapers are wheeled apparatuses having a large laterally extending scraping or cutting blade which shaves off raised areas of ground, the loose or removed dirt being retained within a box structure comprising lateral wings and a curved back panel. Loose dirt is deposited into depressions as the box is pulled along, such that the combination of dirt removal from the raised areas and the dirt deposition into the depressed areas produces a level surface. It is most important that the cutting blade be maintained in a horizontal position to insure a level scrape, but unevenness in the terrain and the speed of the operation combine to produce negative effects known as bouncing, walking or rocking, where the sides of the box and therefore the blade move up and down simultaneously or in alternating fashion, such that the blade alternately cuts too low and then not low enough to produce a level surface. Because of this bounce effect, scraping is usually performed at a very slow pace until a sufficient amount of dirt is accumulated in the box to preclude the problem--the weight or mass of the accumulated dirt tending to negate or diminish the bounce effect. When leveling large areas, maintaining this extremely slow pace is time-consuming and costly in terms of man-hour expenses, so it is highly desirable to correct the bounce effect problem in a manner which allows the box scraper to be pulled at a much higher speed during the leveling operation.
Prior attempts to address this problem include mounting fixed skid shoes or skid plates to the box, the tongue or the wheel suspensions of the scrapers, the skid shoes or plates providing additional contact points with the surface, but this adaption has been shown to reduce the negative effects only slightly. An improved approach has been to provide the skid shoes with damping means, such as springs or shock absorbing pistons, but the configuration and location of the shoes has not been optimized. Examples of such apparatuses are shown in U.S. Pat. No. 5,307,570 to Brown, U.S. Pat. No. 5,072,531 to Pronovost et al., U.S. Pat. No. 4,389,800 to Goby, U.S. Pat. No. 4,125,950 to Mashford, and U.S. Pat. No. 1,968,412 to Lull. The prior art typically teaches the use of skid shoes of relatively small surface area, with the skid shoes located to the rear of the cutting blade.
It is an object of this invention to provide a stabilizing means for dirt scrapers which alleviates the problem of bounce, by providing a pair of stabilizing rails of relatively large surface contact area, where the rails are mounted in a pivoting manner, laterally external to the side wings of the box, such that the rails extend along the base of the wings. The stabilizing rails are provided with damping means, such as shock absorbing pistons, to reduce shocks encountered during the leveling operation, thereby limiting or eliminating the negative bounce effects, enabling the scraper to be pulled at a much higher speed than normally available. Upward travel limiting means are also provided such that the amount of upward movement of the stabilizer rails can be controlled in order to maintain the lower surface of the rails at a desired height relative to the cutting blade. Furthermore, the stabilizing rails act to maintain the loose dirt within the box by precluding lateral movement of the removed dirt out from under the wings when they are slightly off the ground surface, thus preventing the formation of wind rows--a pair of raised ridges of loose dirt laid down on either side of the box portion of the scraper paralleling the direction of travel. These and other objects not expressed at this time are to be accomplished as described below.